Building the seabios defconfig on a 64-bit Debian Wheezy system I'm seeing:
Compiling (16bit) out/romlayout.o src/romlayout.S: Assembler messages: src/romlayout.S:285: Error: expecting string instruction after `rep' make: *** [out/romlayout.o] Error 1
That line is: // Acquire lock and take ownership of shared stack 1: rep nop
I've also checked the preprocessed version and the nop isn't being disappeared or anything like that.
This is with 083ee297ef88d "ohci: Update usb command timeouts to use usb_xfer_time()". I don't see it with the rel-1.7.5 tag.
git bisect has fingered 0673b7870063a ""smp: Replace QEMU SMP init assembler code with C; run only in 32bit mode.", which makes sense since it made those additions to romlayout.S
Other than a compiler bug I can't think what might be going on. Debian Wheezy has gcc 4.7.2 and binutils 2.22.
Ian.